<div class="cats-box">
    <div class="cats-list">
        {volist name="cats" id="cats"} 
        <div class="item">
            <h3>
            <a href="{$cats.link}">{$cats.title}</a>
            </h3>
            {notempty name="$cats['items']"}
            <div class="item-list clearfix">
                <ul class="subitem">
                    {volist name="cats.items" id="child"}
                        <li><a href="{$child.link}">{$child.title}</a></li>
                    {/volist}
                </ul>
            </div>
            {/notempty}
        </div>
        {/volist}
    </div>
</div>